1. Field of the Invention
The present invention relates to a method and an apparatus for IEEE 1394 bus analysis used in product development of a 1394 bus interface circuit.
2. Description of the Related Art
A high speed serial bus conforming to the IEEE 1394 standard (hereinafter referred to as 1394 bus) has been adopted between electronic equipment, for example, between a computer and its peripheral devices, in order to transfer data at a high speed through interconnections each having a small number of electrical lines.
For example, as shown in FIG. 13, in order to transfer data between a computer 10 and a digital video camera 11, 1394 bus interface circuits (nodes) 12 and 13 are connected to the computer 10 and the camera 11, respectively, and a 1394 cable 14 is connected therebetween. The circuits 12 and 13 are configured in different ways depending on configurations of respective interface circuits provided to the computer 10 and the camera 11. When developing the 1394 bus interface circuit 13, there is a need to capture and analyze data on the 1394 cable 14.
In the prior art, as shown in FIG. 14, a 1394 bus analysis interface circuit 15 was disposed between the circuits 12 and 13, a 1394 cable 14A was connected between the circuits 13 and 15, while a 1394 cable 14B was connected between the circuits 12 and 15, and a 1394 bus analysis apparatus 16 was connected to the circuit 15, thereby verifying data on the 1394 bus.
However, since the 1394 bus analysis interface circuit 15 is connected between the interface circuits 12 and 13, the analysis is carried out events different from that on a bus in an actual system.
Further, although the maximum number of nodes according to the specifications of the IEEE 1394 standard is 63, there is a system in which the number of nodes is limited to 2, in which case the 1394 bus analysis interface circuit 15 cannot be connected as shown in FIG. 14.
Accordingly, it is an object of the present invention to provide a method and an apparatus for an IEEE 1394 bus analysis, capable of analyzing an event on a bus between electronic equipment""s of a system used actually.
In one aspect of the present invention, there is provided an IEEE 1394 bus analysis method comprising the steps of: preparing an IEEE 1394 bus interface circuit which includes a physical layer circuit connected to an IEEE 1394 bus; and a link layer circuit connected to the physical layer through signal lines in order to transmit to and receive signals from the physical layer, receiving data from the signal lines; storing the received data; and analyzing the stored data.
With this aspect, since a portion receiving signals from the signal lines is not a node of the IEEE 1394 bus, an analysis can be carried out on events on the IEEE bus in the same system as that used actually.
In another aspect of the present invention, there is provided an IEEE 1394 bus analysis interface circuit comprising: a physical layer circuit, connected to an IEEE 1394 bus, having a link power status signal input, the link power status signal input being fixed inactive to function as a repeater; and a data capture circuit, connected to the physical layer circuit through signal lines, capturing data on the signal lines for data analysis.
With this aspect, on a bus reset conforming to the IEEE 1394 standard, a self ID packet including information of link-off (L=xe2x80x980xe2x80x99) is outputted from the physical layer circuit onto the 1394 bus, and the physical layer circuit functions as a repeater, thereby an analysis can be carried out on events on the IEEE 1394 bus in the same system as that used actually. Further, a bus analysis can be performed on any system using the IEEE 1394 bus.
Other aspects, objects, and the advantages of the present invention will become apparent from the following detailed description taken in connection with the accompanying drawings.